Resilient synthetic yarn



June 12, 1945. J DWE 2,378,183

/ RESILIENT SYNTHETIC YARN Filed Oct. 9, 1941 M x W0 4 N /N R a O Cm .w R i H M m a J 2 W 0v c 2 s W W c m m in E n T W W M 6 ms 0 w a C m 5 w w 5 E 000m. QMEMQ Qmq Qkvwm w 4. 5 E R R W. 0

Patented June 12,

I UNITED STATES.

PATEN'l OFFICE nnsnmn'r SYNTHETIC YARN John R. Caldwell, Kingsport, Tenn; assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Q 3 Application October 9, '1941, Serial no. 414,265

4 Claims. (c1. 260-14) As is well known, yarns and fibers produced I from synthetic materials such as. viscose, cellulose derivatives and resins differ in many respects from natural products such as silk, cotton, wool and the like. It is also known that synthetic yarns difier widely among themselves in .physical and chemical properties, some having certain inherent characteristics which make them particularly w ll adapted for certain uses, while other yarns have characteristics which render them unsuitable for such uses. From the earliest beginningsof the synthetic yarn industry, research has constantly been going on with the object of so modifying such artificial materials as more closely to simulate or duplicat the valuable properties of natural fibers. To the credit of the researchworkers in this field, it may be said that in many instances, not only have the properties of natural fibers been duplicated in synthetic yarns, but actually have been improved upon. On the other hand, it has been found impossible to duplicate certain other properties in synthetic yarns,

The difliculties involved in dealing with syn-- thetic materials produced from cellulose derivatives, such as cellulose acetate and similar cellulOse organic acid esters, as well as the cellulose ethers, are multiplied because of the-plastic or semi-plastic nature of. the material and its susceptibility to cold flow. In general, it may be said that to attain any given property or combination of properties in'such a yam, it is always 40 necessary to balancea number of factors one against the other. For example, it may in a given instance be quite easy to produce a yarn having high tensile strength and other desirable properties and at the. same time fail to attain the desired degree of stretch or stretchability of the yarn to make it a practical commercial product. Likewise, it maybe a relatively simple matter to crimp a cellulose derivative'yarn by adverted to.

20 hyde, urea and formaldehyde and others.

the problem ofproducing a satisfactory type of synthetic yarn or fiber which will have most of the desirable characteristics of natural wool.

This is particularly true of attempts to obtain a 5' cellulose derivative yarn which willpossess' high ,crimp retentivity and springiness and will at the same time be susceptible of crimping by mechanical means under the influence of heat and pressure without otherwis being adversely afiected.

10 In recent years, literally hundreds of attempts have-been made to solve this problem andthe patent and technical literature contains a multitude of references to the use of various and sun dry expedients.

yarn with a solution of a resin. Included among the'resinssuggested for the purpose arethe socalled heat-hardening resins such as these obtained by condensing phenol and formalde- Another suggestion has been to incorporate such resins or solutions of resins in the spinning solution from which the yarn is produced. In either case the yarn containing the resin or resin-form- 25 ing components is subjected to some sort of physth yarn will be stiffened and thus rendered resilient.

' Notwithstanding the many expedients suggested for the production of this type of yarn, none of them, to the best of my knowledge and belief,

has offered-a complete solution of the problem.

While synthetic yarns have heretofore undoubtedly been stiffened by impregnation with, or by formation in situ of, heat-hardening resins in the manner just referred to, it appears that in no instance have all of the various factors necessary for the production of a, satisfactory com-' mercial yarn of this type been so balanced or coordinated as to give the desired product. Presumably, this has been due to a failure upon the part of research workers in this field fully to appreciate the theoretical considerations involved. In order more fully to explain the advance in the synthetic yam art represented by the present invention, this matter of theory will now be briefly lulose typified by cellulose acetate, cellulose acetate propionate and the like, possess relatively 55 little elasticity as compared to natural fibers such One of the most common of 16 these expedients is to impregnate'a preformed as silk and wool. is stretched to an elongation of approximately and subsequently released, it will return sub- For example, if natural sill:-

These objects are accomplished by the following invention which, in its broader aspects, comprises combining with a cellulose derivative yarn as an integral part of the internal structure or the yarn material itself, a specific type of thermosetting resin in certain specific proportions and To employ the language of mechanics, these ma- 7 class of non-elastic substances, that is; they show a well-defined yield point and readily undergo permanent deformation.

The molecular or structural units or micelles of which cellulose derivative fibers are-composed have relatively low cohesive forces. Furthermore, they are of such nature that under conditions of stress, these molecular units slide past each other and assume new permanent positions when the stress or applied force is released. These slippage planes or areas of relatively low cohesive force contribute in a considerable degree to the relatively large permanent deformation observed in cellulose derivative fibers.

As will be more fully explained by reference to specific examples appearing hereinafter, I have found that the yield point characteristics of a cellulose derivative fiber are closely associated with the properties of stiffness and resiliency. Textile materials possessing these properties are described as having a, wiry or springy hand or 'feel. Wool is a good example of a natural product having such properties. For example, if a mass of wool fiber is compressed and then released, it will spring back almost immediately to substantially its original volume. It is this characteristic which gives woolen fabrics their strength and wearing qualities. Ari analysis of the stress-strain curve for wool shows that there is no well defined yield point as found in the case of cellulose acetate or other cellulose derivative synthetic fibers. Hence, it must=be concluded that the closer the stress-strain curve ,of such synthetic fibers approaches that of wool, the closer will be the resemblance of the synthetic product to the natural product as to resiliency, elasticity and similar properties.

This invention has as an object to provide a cellulose derivative yarn or fiber having resiliency.

elasticity and other properties comparable to wool and other natural fibers. provide a cellulose acetate or other cellulose-derivative yarn which is susceptible of permanent mechanical crimping or other deformation with? out the loss of any or the yams desirable phy ical properties. process of preparing a sprin s. resilient, elastic cellulose derivative yarn or fiber of the type specified. A specific object is to improve upon known processes of producing resin-containing synthetic yarns and to obtain a product possessing properties superior to those of known synthetic yarns. Other objects will appear hereinafter.

A further object is to A still further object is tov provide a' under such conditions that a permanently resilient yarn will be obtained. It is desired particularly to point out that the resin after formation under carefully controlled conditions is added to the spinning solution and thus is incorporated in the yarn structure itself, as differentiated from impregnation of a preformed yarn with the resin.

It should be noted at this point that the present invention involves the use of a very special type of resin which 'must meet certain specific. requirements. After an extensive investigation I have found that in order to meet such requirements, the resin must havethe following characteristics: (a) it must be soluble in acetone or whatever solvent is employed for dissolving the cellulose ester in making up the spinning solution, (b) it must be compatible with the cellulose ester in the dope, (c) it must be chemically inert toward the cellulose ester, (d) it must be compatible with the cellulose ester when the solvent is evaporated, (c) it must be sufilciently light in color to avoid discoloring the yarn, (I) it must be convertible to a form which will be resistant to washing, ironing and other textile processing treatments, (g) it must be thermosetting under such conditions of time and temperature as will not injure the cellulose ester fiber and (h) it must be capable of forming a continuous rigid structure in the yarn which exerts a stifiening and reinforcing action throughout the body of the material. Y

As will be readily appreciated, many resins fall short in one or more respects of meeting the above specifications. In fact, in carrying out research on this problem. I have investigated phenolforinaldehydeand urea-formaldehyde resins, the so-called alkyd resins of the phthalic anhydride-polyhydric alcohol type, polymeric derivatives of acrylic acid, polymeric derivatives of vinyl acetate and vinyl chloride and resins derived from drying oils. All of these classes of resins were found deficient in one or more of the essential requirements. For example, many alkyd resins showed excellent compatibility but required excessively high temperatures for curing. Phenol formaldehyde resins were satisfactory from the standpoint of compatibility and curing temperature but lacked sufilcient reinforcing action. Urea formaldehyde resins cured rapidly to hard, tough products, but tended to be incompatible with the cellulose ester material.

After many experiments were carried out, I found that a resin' con'densation product formed by the interaction of phenol, urea and formaldehyde under carefully controlled conditions met each and everyone of the above requirements and made possible the production ofa superior yarn product having the desired qualities of springiness, resiliency, elasticity and'the like- The resin condensation products contemplated by my invention may be defined as products I and para-cresol.

urea, thiourea, or mono-N-s'ubstitutd urea" or thiourea, (c) 3 to 5 molecular proportions of, formaldehyde;

In addition to phenol many types of alkyl sub; 5 .stitutedphenol derivatives having two free ac-fitive groups are suitable for the process, for example: ortho-, par-a-, or meta-cre'sol; 1,3,5

xylenol; p-tertiary butyi phenol; z-ethyl phenol, 1 etc; For economic reasons it is sometimes prefer able to usea mixture of substituted phenols, as

for example, the commercial mixture of meta-,

Resins with improved color characteristics are obtained if the phenols are distilled Just prior to use.

Although the best resins are produced with urea or thiourea, it is possible to use N-substituted ureas as for example N-butyl urea, N-ethyl urea.

etc. Formaldehyde may be employed in the form of 40% formalin or as an aqueous suspensionof paraformaldehyde. The reaction is carried out within a temperature range from 70 C. up to the atmospheric pressure boiling point of the reac'- tion mixture.

Suitable resins are formed only under alkaline conditions, and I have found thatv amines are superior to mineral alkalis as catalysts, although either may be used, Among typical a'mine'catalysts maybe mentioned ammonia, mono-, di-.

and ,trimethyl amine, the corresponding, ethyl i amines, pyridine, higher amines such as butyl amines, amyl amines and similar amines. :I'

have found that the type'of catalyst employed exerts a profound influence upon the properties of the resin. Among the catalysts just referred to, a mixture of monobutylamine and ammon a proved to be a highly specific catalyst that gave resins considerably superior to those made with other alkalis. In carrying out the condensation reaction a sumcient amount of the catalyst is added at the beginning to maintain a pH value of 7.5-9.5 throughout the entire. course of-the reaction.

The time of reaction varies considerably with the nature and proportions of the components; For example: meta-cresol will react faster than the para derivative. In general, the condensation is carried to a point where the product is soluble in acetone and curable in three to four In employing the resin for the manufacture Of a resilient type of yarn in accordance with my.

invention. anywhere from 23-30% and preferably -20% of the resin based on the weight of the cellulose ester, may be employed.

alias;

' -ly may, resilient am when empldyed in at;

f'c'o'rdance with'the invention, It is desired'to emphasi ze the factthateach of these require- [meats must be met and that deficiencyfin a single'one immediately eliminatesthe resin from consideration. {Itfis thus evident that a resin suitable .for'. the purposes outlined herein is a highly specific composition possessing'weil-defined and'closely-restricted properties and canhas been treated; both in accordance with the f invention. and without" such treatment.

cordance with the invention;

, Fig. 2jis -a graphical representation of tha -re "siliency of a cellulose organic acid ester yarn, bothfwith, and without, a resin e'r'nployedin ac- 0 Example 1 A mixture'having' the following composition:

1 v Parts-by weight Mixed metaand para-cresolsne Urea 8 440% aqueous solution) formaldehyde 90 r "(,28%,aqueou s solution) ammonium hydroxis heated to boiling under reflux and maintained at this temperature for twenty to thirtyminutes. Part of the resin separates as a viscous syrupwhich settles. to the bottom of the, reaction vessel. .The mixture is then evaporated at reduced pressure to a water content of 25 as determinedby distillation, with toluene. The

. hours at 100-125 C. This point can be determined only by trial and error because of the many variables which influence the reaction rate.

final product is avis'cous syrup soluble in ace-,

tone. For convenience in handling, the resin is dissolved in-acetone to, form a 30%-60% semtion. i

For-preparation of the-yarn, a spinning solution or done is Partsbyweight Cellulose acetate 25 Acetone"; A '72 .ReSlIl. Q 3

As will be more fully set 'forth hereinafter, the resin-bearing yarn is cured at an appropriate ing temperature is within the range of 90425". C. At this temperature, curing ,takes place in 1-3 hours depending upon the nature of the specific resin used. Curing will take place more rapidly at temperatures above 125 C. but there is danger of discoloring or tendering the yarn. In some cases, as with resins containing an appreciable amount or metacresol. a curing temperature of IO-80 C. is suitable. The optimum curing range of temperature and time must be determined separately for each resin type because of individual differences in reactivity.

I wish to particularly point out that only resins prepared in accordance with the above descriptemperature. In general, themost practical cur- .morpholine acetate, amylamine acetate and tion meet each and every one of. the eight es-" sential requirements of a resin to give an actualhave foundthat it is often advantageous to employ a curing catalyst with theresins. The

catalyst may be incorporated in the resin solution prior-to mixing with the spinning dope, or it may, be added directly to the spinning dope.

.Salts'formed by reacting certain amines. with weak acids are .well suited as catalysts. Among these may-be mentioned -.butylamine propionate.

morpholine 'borate: The catalyst is added to the extent of 1%-5 based on the weightfof the resin. For this particular resin, 2% morpholine acetate isiused as catalyst,

A dope prepared as just described extruded into an evaporative atmosphere (dry .sp'innin'z) 'or precipitating bath (wetspinning) by-known methods, as, ;forexample, the processes described in the s patents to Stone 2,0 0,048 and 7 2-,000,049, .-and wound onto a suitablepackage. Theyar'n so formedis', then heated at a "tem- .perature-of 130 'C. from one'to five hours to curethe resin. It may be heated in the form ide -8 prepared'having the following of skeins, or on spools, bobbins, etc. It isoiten I advantageous to use bobbins or. spools with perforated cores to promote circulation of air.

Yarn prepared according to this method has a relatively high yield point and possesses improved elastic properties. In Fig. 1 of the draw-- or hand.

ing the stress-strain curve illustrates the influence of the resin on the elastic properties oi the' yarn. Curve A is that obtained by testing a cellulose acetate yarn prepared as described above and containing of the resin in accordance with the invention. Curve B is for a similar yarnbut containing no resin It will be observed that the yield point Y'for-yarn containing the resinis 1.00 gram per denier while the yield point Y for the yarn containing no resin is 0.72 gram per denier. resin gives rise to, an improvement of- 39%. It is therefore evident that the presence of the 10% of this particular resin has imparted new Thus the use of and valuable properties to the fiber.) Incidentally, it will be observed that the stretch has been somewhat reduced.

I The fiber produced as described in the preceding paragraphs may be processed on the usual weaving and knitting machinery to give fabrics having excellent fullness of hand. Fabrics prepared from yarn of this type show superior elastic properties and excellent resistance to stretching and sagging. It is notable that many of the resins falling within the scope of my invention raise the melting and/or softening point of the yarn. For example, the melting point of the fiber just-described is 260-262, 0., whereas the yarn without the resin has a melting point of 250-252". This is also an important characteristic of my invention,- the net effectof which is to raise the safe ironing point of a fabric made from such yarn,

as-ra se to'have excellent properties or resiliency, fullness Example 4 A. resin having outstanding properties for use in a spinning solution as outlined in the preceding examples may be prepared from the following composition:

Meta-para cresol grams 20 Urea do 10 Formalin (40%) .450... 90 Cone. ammonium hydroxide --cc..- 5 Monobutylamine cc 2 The mixture is boiled for 20 minutes, then evaporated under vacuum to a water content 0! 20%-30% as shown by boiling toluene extraction.

As will be apparent to those skilled in the art. the impregnated yarns of my invention are useful for many purposes. Because of the high yield point of the material, it is especially suitable for use in fabrics where resistance to crushing is desired, such as in carpets, blankets, velvets, up-

for example. -A mixture having the following composition Parts by weight Urea 8 Thiourea 8 Mixed m-p-cresol 25 40% formalin 90 Diethylamine 1 is worked up by a procedure similar to" thatdescribed in Examples 1 and '2 above. The resin thus produced is incorporated in a spinning solution and yarn spun therefrom in accordance with standard procedure. Following the heat treatment referred to in Example .1, the yarn is found holstery and similar pile fabrics. It is of especial value in the preparation of cut staple fibers, particularly those which are tov be employed as wool substitutes. because of the fact that the resin imparts an appreciable stifiness and elasticity to the yarn and thus gives it an especially resilient hand and a close resemblance to natural wool.

Staple fibers prepared in accordance with the present invention show a markedly improved permanence of crimp because of their high yield point, that is, a much greater load is required to remove the crimp and permanently straighten the fiber than is the.case with ordinary yarns and with other resin-impregnated yarns. A product closely resembling natural wool may be produced by crimping cellulose acetate and other cellulose organic-acid ester yarns, containing resins according to my invention, by the mechanical crimping process described in my copending application Ser. No. 366,887, filed November 23. 1940, and then subjecting the crimped and resinimpregnated yarn to a heat treatment to thermoset the contained resinous materials.

Other uses which the particular properties of my product make possible are as stuiilng or filling for padded articles such aschair cushions, automobile seats and the like. Becauseof its close similarity to wool, the resin-bearing fiber mate- 'rial may also be employed in men's suiting,

v worsteds and similar fabrics.

As will be indicated by the curves of Figs. 1 and 2, yarn prepared in accordance withmy invention and containing 10-20% of phenol-ureaformaldehyde resin gives rise to an appreciable improvement in the yield point of the yarn as compared to yarns not so treated and imparts a stiffer, more resilient feel to the material, thus increasing its resemblance to natural wool. Naturally, the stiffening process results in some loss of stretch, but this is relatively insignificant. I have found, for example, that when 10-20% of resin is employed in the yarn, it g'ivesapproximately 9. 40% increase in the yield point. Tests have shown that it takes 30-40 greater longitudinal stress to remove the crimp from yarn containing 10% resin as compared to normal yarn. Analysis of the stress-strain curve of Fig. 1 shows beyond all doubt that the resin sets up to a semirigid structure or skeleton within the body of the filament which imparts a pronounced stiffening action to the yarn and brings about a significant reduction in the cold flow tendency of the cellulose derivative material.

meat.

Referring to Fig. 1 curve A was plotted from data taken on yarncontaining 10% phenol-urea- J formaldehyde in accordance with my invention.- The yield point is indicated by the letter Y. The

stress-strain curve of the same yarn without the resin is illustrated by the curve B, the yield point of this yarn being indicated by the letter Y1. It

will be seen that, not only does yarn A have a' much higher yield point than yarn B, but that the shape of the stress-strain curve, especially in the vicinity of the yield point is profoundly altered by the presence of the resin.

The property of a fiber to spring back after deformation is best described by the term resiliency. Wool is a typical example of a fiber which possesses resiliency to a high degree. This quality may be measured quantitatively and it found that a cellulose acetate yarn prepared in 10-20% of a phenol-urea-iormaldehyde. resin is considerably more resilient than a similar yarn which does not contain the resin. Typical resiliency curves are shown in Fig. 2. These curves were obtained by plotting the amount of force necessary'to compress a given weight of staple through the distance shown on the horizontal axis. The

' pressure was then gradually removed fromthe staple and it was allowed to recover. Each sample is represented by two curves, the one on the left showing compression, the one on the right showing expansion or recovery. The area en- 1 closed by the two curves is inversely propori' 1 from the group consisting of phenol and alkylsubstituted phenols containing atleast two free active positions on the. nucleus with item 0.15 to accordance with my invention and containing What rennin v 1. A synthetic yarn based on the-weight of the cellulose ester .of' a partially polymerized phenol-urea formaldehyde resin prepared bycondensing under'alkaline conditions 1 molecular proportion of a phenol selected 1.0 molecular proportion of a urea selected from solution, a high degree" of res'ilie'ncy, elasticity, a

springy hand r feel andfa' yieldpoint'"in the.

. neighborhoodof'l gramper denier."

' ing a'cellulose organic acid ester dissolved in a I spinningsolution comprising acellulos'e organic acidester' dissolved in a; volatile solvent and contain n insolution 5'-30% 2. A syntheticyarn spinning solutioncomprisvolatile'solvent'andcontaining in solution 530 based on. the weight of the"; cellulose ester of a I partially polymerized phenol-urea-iormaldehyderesin prepared by condensing 1 molecular proportional to the resiliency or recovery tendency ofl the fiber. That is, if'the fiber were perfectly elastic and returned completely to its original. shape, the compression curve and expansion curves would coincide.

'tion'oi a" phenol selected from the group consisting of phenol and-alkylesubstituted phenols containingIat-least two free active positions on the nucleus with;from '0.15 to 1.0 molecular propor-Q tion of a urea selected from the group consisting 4 of urea and 'mono Nealkyl substituted ureas and The area enclosed be-q tween the two curves thus represents the ener y lost by hysteresis, that is, the difierencebetween the work done to compress the yam and the work given backby the yarn during expansion.

It will be noted that the area enclosed by curves'A plotted from data taken on a yarn con:

taining a phenol-urea-formaldehyde resin in accordance with my invention, is considerably smaller than that enclosed by the curves B plotted resin. This strikingly illustrates the superiority return to its original shape ascompared to an from data taken on the same yarn'containing no mono N-alkyl" substituted th'iourea's and '3-5 i iolje ziilar proportions of formaldehyde, in the presence of aImixture of monobutylamine and ammonium hydroxide as catalyst, said resin being susceptibleof further polymerization under the infi'uence'of heat, said resin in its further polym z' d 11 av h t e 'p operty'oiimp r ns to iy'arn vformed from said solution, a high degree of s iency, elasticity, a, springy hand or'feel and a m t in the nighborh d of 7 denien p 3.- A synthe c yarn spinning solution comprising25pa'rtsby weight of celluloseacetateflz parts 'by" weight ;.acetone and 3 parts by weight of a of the resin-eontainingyarn in its tendency ordinary yarn and shows that it is much-more.

resilient.

It is particularly to be prepared as described above are, in accordance with my invention, added to the spinning solution and cannot be applied to preformed yarn. Thus,the present process is to be diiferentiated from previously known processes wherein preformed yarns, fibers or fabrics are soaked or 1m;

pregnated with resin-forming materials.- Although many proposals have been made for incorporating in a spinning solution a thermoset-j ting resin or the components from which such a resin could be formed in situ, to the best of my knowledge and belief, no practical process for.

obtaining a resilient resin-impregnated yarn has.

ever before been suggested or disclosed in the prior art. Due to the fact that in the present noted that the processtheresinismixedwiththespinningsolutionso that a homogeneous dispersion rsolution thereof is obtained. the resin becomesan integralpartoftheflberstructureaftertheyarnis formed and thus exerts its reinforcing action" throughout the entire cross-section j neighborhood i-i gra ri per n es; r

ofthe ma-- phenol-urea-formaldehyde"resin prepared by 1 boiling for approximatelyzominutes a composi- "w ifAfsynthetic yarn spinningsolutioncoinpris-v T 1 acellulose organicaeidester. dissolved in volatile-solvent and containing 5.430% of Y a pal-' polymerized resin prepared "by condensing 1 molecular-proportion of phenol with from -0.'1 5 to 1.0 molecular proportion of urea and mo-' lecular proportions .of-formaldehyde, said-resin lbeingsoluble-in the solvent,"susceptible.of further 'polymerization under the. influence ofheat in its further polymerized .iorm1, having-the' property of imparting- -,to' yarn formed-from said"solution a high. degreefof-ire'sillency; elasticityis sprinsy hand'or feel'ayield point-in-. the

' o'fonna. 

